Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import *
h,w=map(int,input().split())
a=[input() for _ in range(h)]
b=[[h*w]*w for _ in range(h)]
b[0][0]=1
d=deque([[0,0]])
while d:
    y,x=d.popleft()
    for i,j in([1,0],[-1,0],[0,1],[0,-1]):
        t,u=y+i,x+j
        if 0<=t<h and 0<=u<w:
            if a[t][u]=="." and b[t][u]>b[y][x]+1:
                d.append([t,u])
                b[t][u]=b[y][x]+1
c=sum([i.count(".") for i in a])
print(max(-1,c-b[-1][-1]))